U.S. patent number 8,818,492 [Application Number 13/686,291] was granted by the patent office on 2014-08-26 for apparatus and method for measuring ganglion cells.
This patent grant is currently assigned to Korea Institute of Science and Technology. The grantee listed for this patent is Korea Institute of Science and Technology. Invention is credited to Jin Wook Jeoung, Chulki Kim, Jae Hun Kim, Seok Hwan Kim, Sun Ho Kim, Hyuk Jae Lee, Seok Lee, Taikjin Lee, Ju Yeong Oh, Ki Ho Park, Deok Ha Woo.
United States Patent |
8,818,492 |
Kim , et al. |
August 26, 2014 |
Apparatus and method for measuring ganglion cells
Abstract
An apparatus for measuring ganglion cells may include: a light
generation unit configured to irradiate a first light signal
polarized in a first direction and a second light signal polarized
in a second direction perpendicular to the first direction to a
subject; a reflected light processing unit configured to generate
an amplification signal corresponding to an image of the subject
using a first reflection signal, which is the first light signal
reflected from the subject, and a second reflection signal, which
is the second light signal reflected from the subject; and an image
processing unit configured to measure ganglion cells in the subject
using the amplification signal. The apparatus may be used to count
the number of normal ganglion cells in the retina by measuring a
phase difference of two lights polarized in different directions.
The apparatus may also be used to monitor the progress of
glaucoma.
Inventors: |
Kim; Jae Hun (Seoul,
KR), Lee; Seok (Seoul, KR), Lee; Hyuk
Jae (Goyang-si, KR), Lee; Taikjin (Seoul,
KR), Kim; Sun Ho (Seoul, KR), Kim; Seok
Hwan (Seoul, KR), Jeoung; Jin Wook (Seoul,
KR), Park; Ki Ho (Seoul, KR), Oh; Ju
Yeong (Gimpo-si, KR), Woo; Deok Ha (Seoul,
KR), Kim; Chulki (Samcheok-si, KR) |
Applicant: |
Name |
City |
State |
Country |
Type |
Korea Institute of Science and Technology |
Seoul |
N/A |
KR |
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Assignee: |
Korea Institute of Science and
Technology (Seoul, KR)
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Family
ID: |
50547932 |
Appl.
No.: |
13/686,291 |
Filed: |
November 27, 2012 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20140121530 A1 |
May 1, 2014 |
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Foreign Application Priority Data
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Oct 26, 2012 [KR] |
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10-2012-0119674 |
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Current U.S.
Class: |
600/425; 600/407;
600/476; 600/310; 600/477; 600/558 |
Current CPC
Class: |
A61B
3/145 (20130101) |
Current International
Class: |
A61B
5/05 (20060101) |
Field of
Search: |
;600/407,310,476,477 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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10-2008-0013919 |
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Feb 2008 |
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KR |
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10-2011-0054584 |
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May 2011 |
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KR |
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10-1092376 |
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Dec 2011 |
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KR |
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Primary Examiner: Jung; Unsu
Assistant Examiner: Lamprecht; Joel
Attorney, Agent or Firm: NSIP Law
Claims
What is claimed is:
1. An apparatus for measuring ganglion cells, the apparatus
comprising: a light generation unit configured to irradiate a first
light signal and a second light signal to adjacent regions of a
subject with an offset, the first light signal being polarized in a
first direction and the second light signal being polarized in a
second direction perpendicular to the first direction; a reflected
light processing unit configured to generate an amplification
signal corresponding to an image of the subject using a phase
difference of a first reflection signal and a second reflection
signal, wherein the first signal corresponds to the first light
signal being reflected from the subject and the second reflection
signal corresponds to the second light signal being reflected from
the subject; and an image processing unit configured to measure
ganglion cells in the subject using the amplification signal.
2. The apparatus for measuring ganglion cells according to claim 1,
wherein the image processing unit is configured to measure a number
or density of the ganglion cells.
3. The apparatus for measuring ganglion cells according to claim 1,
wherein the light generation unit comprises: a polarizer polarizing
a light in one direction; and a polarizing prism generating a first
light and a second light to be polarization-rotated by the ganglion
cell from the light that has passed through the polarizer.
4. A method for measuring ganglion cells, comprising: generating a
first light signal polarized in a first direction and a second
light signal polarized in a second direction perpendicular to the
first direction; irradiating the first light signal and the second
light signal to adjacent regions of a subject with an offset;
generating an amplification signal corresponding to an image of the
subject using a phase difference of a first reflection signal and a
second reflection signal, wherein the first reflection signal
corresponds to the first light signal be reflected from the subject
and a the second reflection signal corresponds to the second light
signal being reflected from the subject; and measuring ganglion
cells in the subject using the amplification signal.
5. The method for measuring ganglion cells according to claim 4,
wherein said measuring the ganglion cells comprises measuring a
number or density of the ganglion cells.
6. The method for measuring ganglion cells according to claim 4,
wherein said generating the amplification signal comprises
cancelling a noise component from the light reflected on the
subject so as to extract the first reflection signal and the second
reflection signal to form the image of ganglion cells.
Description
CROSS-REFERENCE TO RELATED APPLICATION
This application claims priority to Korean Patent Application No.
10-2012-0119674, filed on Oct. 26, 2012, and all the benefits
accruing therefrom under 35 U.S.C. .sctn.119, the contents of which
in its entirety are herein incorporated by reference.
BACKGROUND
1. Field
Embodiments relate to an apparatus and a method for imaging and
measuring ganglion cells. More particularly, embodiments relate to
an apparatus and a method for measuring ganglion cells capable of
measuring number, density, etc. of ganglion cells in the retina of
a human or animal eye and thus diagnosing presence and progress of
diseases such as glaucoma.
2. Description of the Related Art
Glaucoma is an eye disease in which the function of the optic nerve
is impaired as the optic nerve is pressed or the blood flow is
restricted owing to raised intraocular pressure. The damage of the
optic nerve leads to visual field loss, which over time can
progress to blindness. Whereas acute glaucoma can be detected early
due to severe pain, chronic glaucoma has few symptoms and, when
symptoms are found, it is generally too late to treat. Accordingly,
it is very important to detect glaucoma early through periodic
examinations.
Since the major cause of glaucoma is damages to ganglion cells, the
progress of glaucoma can be diagnosed by observing the degree of
damage of the ganglion cells. The simplest method is to measure the
intraocular pressure and, if it is higher than the normal
intraocular pressure, treatment for glaucoma is made to lower the
intraocular pressure below the normal level. For example, Korean
Patent Application Publication No. 10-2011-0054584 discloses a
device for measuring the intraocular pressure of a patient for
diagnosis and treatment of glaucoma. However, the diagnosis based
on the intraocular pressure measurement is not so accurate.
Recently, the optical coherence tomography (OCT) technique, whereby
the thickness of the layer of the retina where ganglion cells are
located is measured to diagnose the progress of glaucoma, is
frequently used. In general, it is known that raised intraocular
pressure leads to damage of the optic nerve since the optic nerve
is pressed and, as a result, the ganglion cells connected to the
optic nerve die and the thickness of the layer where the ganglion
cells existed decreases. But, if the decreased thickness of the
layer is measurable by OCT, glaucoma has already progressed a lot.
Therefore, it is difficult to detect glaucoma at an early stage
using this method.
SUMMARY
According to an aspect, the present disclosure provides an
apparatus and a method for measuring ganglion cells, capable of
measuring the number or density of ganglion cells in the retina of
a human or animal eye based on phase difference measurement of two
lights polarized in different directions rather than measuring the
thickness of the layer where the ganglion cells are located.
According to an embodiment, an apparatus for measuring ganglion
cells includes: a light generation unit configured to irradiate a
first light signal polarized in a first direction and a second
light signal polarized in a second direction perpendicular to the
first direction to a subject; a reflected light processing unit
configured to generate an amplification signal corresponding to an
image of the subject using a first reflection signal, which is the
first light signal reflected from the subject, and a second
reflection signal, which is the second light signal reflected from
the subject; and an image processing unit configured to measure
ganglion cells in the subject using the amplification signal.
According to an embodiment, a method for measuring ganglion cells
includes: generating a first light signal polarized in a first
direction and a second light signal polarized in a second direction
perpendicular to the first direction; irradiating the first light
signal and the second light signal to a subject; generating an
amplification signal corresponding to an image of the subject using
a first reflection signal, which is the first light signal
reflected from the subject, and a second reflection signal, which
is the second light signal reflected from the subject; and
measuring ganglion cells in the subject using the amplification
signal.
In accordance with the apparatus and method for measuring ganglion
cells according to embodiments, the ganglion cells in the retina
may be measured by imaging the phase difference of two lights
polarized in different directions. The apparatus and method for
measuring ganglion cells may be used to measure the number or
density of the ganglion cells in the retina of a human or animal
eye and thus to diagnose the presence and progress of glaucoma.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, features and advantages of the present
disclosure will become apparent from the following description of
certain exemplary embodiments given in conjunction with the
accompanying drawings, in which:
FIG. 1 is a schematic diagram showing a configuration of an
apparatus for measuring ganglion cells according to an
embodiment;
FIG. 2 is a block diagram showing a configuration of a light
generation unit of an apparatus for measuring ganglion cells
according to an embodiment; and
FIG. 3 is a block diagram showing a configuration of a reflected
light processing unit of an apparatus for measuring ganglion cells
according to an embodiment.
DETAILED DESCRIPTION
Hereinafter, exemplary embodiments will be described in detail with
reference to the accompanying drawings.
FIG. 1 is a schematic diagram showing a configuration of an
apparatus for measuring ganglion cells according to an
embodiment.
Referring to FIG. 1, an apparatus for measuring ganglion cells
according to the embodiment may comprise a light generation unit
110, a reflected light processing unit 130 and an image processing
unit 150. The light generation unit 110 and the reflected light
processing unit 130 may respectively comprise one or more optical
element for irradiating light to a subject 1 and detecting light
reflected from the subject 1. The subject 1 may be a human or
animal eye. And, the image processing unit 150 may measure ganglion
cells present in the subject 1 using an image obtained from
reflected light.
The light generation unit 110 irradiates two lights polarized in
different directions to the subject 1. In an embodiment, the light
generation unit 110 is configured to irradiate a first light signal
and a second light signal, which are perpendicularly polarized with
respect to each other to obtain a differential interference
contrast (DIC) image of the subject 1.
FIG. 2 is a block diagram showing a configuration of the light
generation unit 110 of an apparatus for measuring ganglion cells
according to an embodiment.
Referring to FIG. 2, the light generation unit 110 may comprise a
light source 112, a polarizer 114, a polarizing prism 116 and an
objective lens 118. However, this is only exemplary and the light
generation unit 110 does not necessarily comprise all the optical
members 112, 114, 116, 118 shown in FIG. 2. That is to say, some
members may be omitted or other additional members may be
added.
The light source 112 may generate a light to observe the subject.
In an embodiment, the light source 112 may be a light-emitting
diode (LED), a fluorescent lamp, a mercury lamp, a sodium lamp, or
the like, but is not limited thereto.
The polarizer 114 may polarized the light generated by the light
source 112 in specific directions. Although the light generated by
the light source 112 oscillates in all directions perpendicular to
the path of the light, it is separated into lights polarized in
specific directions as it passes through the polarizer 114. In an
embodiment, the polarizer 114 may generate a polarization signal by
separating only the light polarized with an angle of 45.degree.
from the light generated by the light source 112.
The polarizing prism 116 may separate the polarization signal
transmitted from the polarizer 114 into two light signals polarized
in perpendicular directions. In an embodiment, the polarizing prism
116 may be a Wollaston prism. Since the Wollaston prism consists of
two layers of crystalline materials, it has different refractive
indices for different polarization directions. According to Malus'
law, the intensity of a polarized light is proportional to the
cosine of the angle between the light's initial polarization
direction and the axis of the polarizer. Thus, the light passing
through the Wollaston prism is separated into a first light signal
and a second light signal having perpendicular polarization
directions. Detailed explanation of the Wollaston prism will be
omitted since they are well known to those of ordinary skill in the
art.
In an embodiment, the polarizing prism 116 may have a crystal
direction having an angle of 45.degree. from the polarization
direction of the polarizer 114. By the polarizing prism 116, the
polarization signal may be separated into a first light signal
polarized with an angle of +45.degree. from the initial
polarization direction and a second light signal polarized with an
angle of -45.degree.. For example, if the polarizer 114 has a
polarization direction with an angle of 45.degree., the
polarization signal generated by the polarizer 114 may be separated
into a first light signal polarized with an angle of 90.degree. and
a second light signal polarized with an angle of 0.degree. as it
passes through the polarizing prism 116.
However, the above-described polarization angle is given only as an
example and the polarization directions of the polarization signal
and the first light signal and the second light signal generated
therefrom are not limited to specific angles.
The objective lens 118 may converge the first light signal and the
second light signal polarized in perpendicular directions on the
subject 1. In an embodiment, the objective lens 118 may be a convex
lens but is not limited thereto. Owing to the characteristics of
the polarizing prism 116, the first light signal and the second
light signal separated by the polarizing prism 116 are not
converged on the subject 1 at the perfectly same region but at
adjacent regions with a slight offset.
In an embodiment, the apparatus for measuring ganglion cells may
comprise a first prism 120 on the light path between the light
generation unit 110 and the subject 1. The first light signal and
the second light signal may be propagated through the first prism
120 and may be converged on the subject 1.
The first light signal and the second light signal may be reflected
on the surface of the subject 1 and/or may be reflected after
penetrating into the subject 1 by a predetermined depth. The first
light signal is reflected on the subject 1 and becomes a first
reflection signal, and the second light signal is reflected on the
subject 1 and becomes a second reflection signal. Since the first
light signal and the second light signal are irradiated to adjacent
but different regions of the subject and then reflected, the
lengths or refractive indices of light path of the first light
signal and the second light signal become different after the
reflection. The difference in light path causes phase difference of
the first reflection signal and the second reflection signal. For
example, of the first light signal and the second light signal, the
signal reflected at a relatively thicker region may have a relative
phase delay with respect to the other.
The first reflection signal and the second reflection signal
reflected on the subject 1 may be reflected on the first prism 120
and incident on the reflected light processing unit 130. The
reflected light processing unit 130 may generate an amplification
signal corresponding to an image of the subject 1 from the first
reflection signal and the second reflection signal. The reflected
light processing unit 130 may convert the first reflection signal
and the second reflection signal to have the same polarization
direction and convert the phase difference of the first and second
light signals arising as the first and second light signals passes
through the subject 1 to a change in amplitude.
FIG. 3 is a block diagram showing a configuration of the reflected
light processing unit 130 of an apparatus for measuring ganglion
cells according to an embodiment.
Referring to FIG. 3, the reflected light processing unit 130 may
comprise a noise canceller 131, a converging lens 132, a polarizing
prism 133 and a polarizer 134. However, this is only exemplary and
the reflected light processing unit 130 does not necessarily
comprise all the optical members 131, 132, 133, 134 shown in FIG.
3. That is to say, some members may be omitted or other additional
members may be added.
The noise canceller 131 may cancel a noise component from the light
transmitted from the first prism 120 and extract the first
reflection signal and the second reflection signal. For example,
the noise component may be a reflected light component owing to the
region other than the retina, e.g. the crystalline lens, from the
signal included in the light reflected on the subject 1. The
cancellation of the noise component may be performed by any known
or to-be-developed noise processing technique, without being
limited to a specific technique.
The converging lens 132 may converge the first reflection signal
and the second reflection signal with the noise component cancelled
by the noise canceller 131 on the polarizing prism 133. In an
embodiment, the converging lens 132 may be a convex lens but is not
limited thereto.
The polarizing prism 133 may combine the first reflection signal
and the second reflection signal into one light having the same
polarization direction so as to generate an amplification signal.
In an embodiment, the polarizing prism 133 may be a Wollaston prism
like the polarizing prism 116 of the light generation unit 110. For
example, if the first reflection signal is polarized with an angle
of 90.degree. and the second reflection signal is polarized with an
angle of 0.degree., the amplification signal combined therefrom by
the polarizing prism 133 may have a polarization direction with an
angle of 135.degree.. The first reflection signal and the second
reflection signal reflected on the subject have a phase difference.
The interference owing to the phase difference leads to a change in
amplitude of the amplification signal.
The amplification signal may pass through the polarizer 134 and be
transmitted to the image processing unit 150. The polarizer 134 may
have a polarization direction perpendicular to that of the
polarizer 114 of the light generation unit 110. For example, if the
polarization direction of the polarizer 114 is 45.degree., the
polarization direction of the polarizer 134 may be 135.degree.. The
polarizer 134 may prevent the first and second light signals
generated by the light generation unit 110 from being directly
incident on the image processing unit 150 without being reflected
on the subject. On the other hand, since the amplification signal
generated from the first and second reflection signals is polarized
with an angle of 135.degree., it may pass through the polarizer 134
and be incident on the image processing unit 150.
Since the first and second reflection signals have been reflected
at the adjacent regions with a slight offset, the amplification
signal generated therefrom is not a perfectly aligned single image
but an overlap of two images with a slight offset. If the first
light signal and the second light signal have passed through the
regions of the subject having different thicknesses or refractive
indices, a phase difference occurs between the first and second
reflection signals and the portion having the phase difference
appears brighter or darker than other portions owing to
interference in the overlapped amplification signal. Accordingly,
even if the subject 1 comprises a transparent material such as the
retina, the image of the subject 1 exhibits contrast due to the
phase difference.
The image processing unit 150 may measure ganglion cells present in
the subject 1 using the amplification signal. The image processing
unit 150 may observe the size and shape of the cells in the retina
using the amplification signal and may count the cells that satisfy
a given condition or measure a density thereof. For example, the
image processing unit 150 may determine the presence or degree of
glaucoma by measuring the number or density of normal ganglion
cells in the retina. The measuring of the number or density of the
cells by the image processing unit 150 may be performed by any
known or to-be-developed image processing technique, without being
limited to a specific technique.
In an embodiment, the apparatus for measuring ganglion cells may
comprise a second prism 140 on the light path between the reflected
light processing unit 130 and the image processing unit 150. Part
of the amplification signal generated by the reflected light
processing unit 130 may be reflected on the second prism 140 and
incident on the image processing unit 150. Meanwhile, another part
of the amplification signal generated by the reflected light
processing unit 130 may pass through the second prism 140 and be
transmitted to an external image observation device (not shown).
For example, the image of the subject 1 generated from the
amplification signal may be transmitted to the external image
observation device with predetermined time intervals or upon the
request of a user. Also, the image may be provided, for example,
together with the number of the cells in the layer of the ganglion
cells through software processing similar to that performed by the
image processing unit 150.
Using the apparatus for measuring ganglion cells according to
embodiments, it is possible to observe the subject through an image
generated using two reflected lights having different polarization
directions, using contrast in the image generated from interference
caused by the phase difference. For example, the apparatus for
measuring ganglion cells may be used to measure the number or
density of normal ganglion cells present in the retina and thus to
diagnose the presence and progress of glaucoma.
Since it is possible to observe the ganglion cells using the
apparatus for measuring ganglion cells according to embodiments, it
is possible to directly monitor the decrease of ganglion cells due
to glaucoma. This is distinguished from the conventional optical
coherence tomography (OCT) technique wherein the thickness of the
layer where the ganglion cells are located is measured, not the
individual ganglion cells. Accordingly, the apparatus for measuring
ganglion cells according to embodiments allows diagnosis of
glaucoma at an earlier stage as compared to the conventional
OCT-based measurement.
Further, the apparatus for measuring ganglion cells according to
embodiments is not limited to the diagnosis of glaucoma but is also
applicable to other diseases of the retina. And, the apparatus for
measuring ganglion cells according to embodiments may be used as an
auxiliary apparatus during surgery. For example, the apparatus for
measuring ganglion cells may be used to image retinal cells and the
imaged retinal cells may be used as marker during surgery. In
addition, the apparatus for measuring ganglion cells may be used to
monitor the progress of retinal diseases and investigate the
diseases in cellular level using images.
Hereinafter, a method for measuring ganglion cells according to an
embodiment will be described. A method for measuring ganglion cells
according to the embodiment may be performed using the apparatus
for measuring ganglion cells described above referring to FIGS. 1
through 3.
A first light signal polarized in a first direction and a second
light signal polarized in a second direction perpendicular to the
first direction may be generated. For example, a polarizer may be
used to polarize a light in one direction and the light that has
passed through the polarizer may be passed through a Wollaston
prism to generate a first light signal and a second light signal
having perpendicular polarization directions. The generated first
light signal and second light signal may be irradiated to a subject
and reflected on the surface of the subject and/or may be reflected
after penetrating into the subject by a predetermined depth
An amplification signal corresponding to an image of the subject
may be generated using a first reflection signal, which is the
first light signal reflected from the subject, and a second
reflection signal, which is the second light signal reflected from
the subject. In an embodiment, a noise component may be cancelled
from the light reflected on the subject and the first reflection
signal and the second reflection signal may be extracted. An
amplitude of the amplification signal may be determined based on
interference caused by a phase difference of the first reflection
signal and the second reflection signal.
Then, ganglion cells present in the subject may be measured using
the amplification signal. For example, the number or density of
normal ganglion cells in the human or animal retina may be measured
to diagnose the presence and progress glaucoma.
While the present disclosure has been described with respect to the
specific embodiments, it will be apparent to those skilled in the
art that various changes and modifications may be made without
departing from the spirit and scope of the disclosure as defined in
the following claims.
* * * * *